1. Field of the Invention
The present invention relates to a decompressor that facilitates the starting of an internal combustion by opening an engine valve to release the pressure compressed by a piston at the start of the engine.
2. Description of Background Art
An example of known decompressors for an internal combustion engine includes a decompression shaft and a decompression pin (decompression plunger). See, for example, Japanese Patent Application Publication No. 2006-144627. The decompression shaft is inserted in an insertion hole of the camshaft in the axial direction. The decompression pin, on the other hand, is disposed in a pin hole (plunger hole) formed in the camshaft orthogonally to the axial direction. The decompression pin thus disposed is movable inside the pin hole. The decompression shaft and the decompression pin engage with each other. With a rotational movement of the decompression shaft, the decompression pin moves between the decompressing position, wherein the decompression pin opens the engine valve, and the decompression-cancelling position, wherein the decompression pin does not open the engine valve.
In the decompressor disclosed in Japanese Patent Application Publication No. 2006-144627, the decompression shaft is inserted in the insertion hole in the axial direction so as to be removable from the insertion hole. An eccentric protruding portion is formed in an end portion of the decompression shaft, from which end portion the decompression shaft is inserted into the insertion hole. The eccentric protruding portion engages with a recessed groove which is formed in the side surface of the decompression pin.
A centrifugal weight is provided at the other end of the decompression shaft. The swinging movement of the centrifugal weight makes the decompression shaft rotate. The whirling of the eccentric protruding portion, which moves along with the rotation of the decompression shaft, moves the decompression pin in the radial direction of the camshaft. The decompression pin thus moved appears above the cam face of the camshaft.
The position where the decompression pin sticks out of the cam face is the decompressing position to open the engine valve, while the position where the decompression pin submerges below the cam face is the decompression-cancelling position to keep the engine valve closed.
When the drive mechanism that drives the decompression shaft is removed from the camshaft during maintenance work on the internal combustion engine or the like, or in a similar case, the decompression shaft, which is designed to be removably inserted in the insertion hole, may possibly fall out of the camshaft. When the decompression shaft actually falls off, the eccentric protruding portion may possibly disengage from the recessed groove of the decompression pin. When this happens, the decompression pin may possibly fall off as well. As a consequence, the maintenance work is difficult.